1. Field of the Invention
The present invention relates to a vehicle wheel supporting structure for mounting a wheel through a double-row tapered roller bearing on an end of an axle.
2. Prior Art
The vehicle wheel supporting structure should be proof against muddy water to a degree, and accordingly, a higher sealing capability is required. In the case of a double-row tapered roller bearing, muddy water can penetrate into the bearing via two passages; i.e., along (a) mating surfaces of an inner ring and a seal slinger and (b) inner periphery of the inner ring (see FIG. 3A). Conventionally, such a sealing structure is known in which an X-ring is fitted to a chamfer of the inner ring so that muddy water may not penetrate through any clearance between the axle and the inner ring (see FIG. 3B). However, in a severe situation of use exposed to splashes of muddy water all the time, the conventional structure cannot completely prevent muddy water from penetrating through passage (a) along the mating surfaces of the inner ring and the seal slinger.
It is hence an object or the invention to provide a vehicle wheel supporting structure which is proof against muddy water.
It is another object of the invention, to prevent tapered rollers from skewing in favor of improved endurance of the double-row tapered roller bearing used in the vehicle wheel supporting structure.
The term skew of a roller means tilting of the roller with respect to its specified axis of rotation. Crowning is a slight convexity in the contour of a raceway surface and/or the generator of a roller for the main purpose of prevention of a concentrated load, or an edge load, in the contact area between a race ring and a roller, as is well known in the technical field of bearings. For example, in a tapered roller bearing for use in an axle unit of an automobile, both raceway surfaces and the rolling contact surface of a tapered roller are crowned in order to avoid any edge load on the raceway surfaces under a high moment load. In particular, in the raceway surface of an inner ring on which a high contact pressure acts, cut crownings at opposite ends are formed in addition to center crowning. Considering the distribution of contact pressure, generally, the amount of crowning of the larger diameter side cut crowning is set larger than that of the smaller diameter side cut crowning. Accordingly, the point at which the rolling contact surface of the tapered roller comes in contact with the raceway surface of the inner ring is spaced apart from the point at which the rolling contact surface of the tapered roller comes in contact with the raceway surface of the outer ring in the direction of axis of the tapered roller (see FIG. 8A). Misalignment of the contact points causes skew of tapered rollers.